Sennheiser was kind enough to lend me their HD 700 for a home demo. And as you know, I already own the HD 650 (silver drivers) to compare them to. And thankfully, Sennheiser has also agreed to lend me their HD 800 in a few days, for a more thorough side by side comparison. But that is best left to another review.

I'm not sure whether these HD 700 headphones have been burned in or not. But. Neither do I care. Because I'm not a big believer in burn in making a radical difference to the sound. At least in the majority of cases. Anyway, just mentioned this to explicitly state that I've no idea.

How much time have I spent with Sennheiser's HD 700 so far?

Not much. Less than 24 hrs in fact. But. I've already listened to a few songs I'm reasonably familiar with.

So. This isn't a review done after extensive testing. But. I've tried to be as accurate as possible.

How much time have I spent with the HD 650 and the rest of my setup?

At least over 2 years or so. Maybe longer. So that shouldn't hinder this review.

The Setup

Headphones: HD 700 (2012), HD 650 (silver drivers)

Headphone Amplifier: Project Ember v1.0 (just tried a single tube, Marconi 6dj8 is what I recall from memory)

DAC: Asus Essence One Muses Edition

Transport: Asus Essence STX SPDIF to the PC

The HD 650 was tested with and without Sonarworks. Sonarworks is a VST plugin that neutralises the tonality of supported headphones. Sonarworks doesn't support the HD 700 yet.

Music

Bollywood (Arijit Singh etc)

Mozart (very little)

I'd like to sum up the basic advantages of each headphone over the other, before I proceed to a more detailed review. So those in a hurry can still quickly get to know the overall gist in brief.

Advantages of the HD 700 over the HD 650

Way more comfortable. In fact, the HD 700 is so comfortable that that alone justifies twice the price over the HD 650 if you consider them equals otherwise.

There is something that makes them sound less natural and less musical.

The tonality isn't as neutral; the vocals are a bit upfront as compared to the rest.

Advantages of the HD 650 over the HD 700 (Many of these advantages may be audible only if you have Sonarworks, as that takes the experience to another level.)

More musical, lush, smoother and sweet overall.

The bass isn't as tight but perhaps more natural and with greater punch.

The treble isn't as sharp; it is smoother.

More suitable for extended listening.

It has most of the pros of the HD 700 but not quite to the same level. In terms of technical prowess, it is what it is. An outdated flagship.

Now.

You're probably waiting for a more in-depth comparison between the two. And that is exactly what I'm coming to now.

HD 700 v/s HD 650 (with Sonarworks) - One on one

Sound signature

HD 700

The HD 700 isn't as connect in tonality. But it is a very enjoyable sound signature nevertheless. The bass is super tight. The treble is lively and slightly Brit. The vocals are upfront. The sound is very tight overall. Everything is very tight.

HD 650

More neutral and balanced. Sounds smoother and sweeter, more musical. Nothing stands out even though the vocals are delicious.

Soundstage & Imaging

HD 700 > HD 650

The difference isn't huge. But is still significant. And easily audible. Can be a deal breaker for many once they get used to the HD 700.

I'm not too certain about the imaging. But. I think the HD 700 has an edge there as well.

Vocals

HD 700

More articulate and realistic. They have better resolution and are more detailed. Also more upfront. Crisper.

HD 650

More musical, rounded and smoother. But not quite of the same stature.

Bass

HD 700

A lot tighter. Perhaps artificially tight. Not sure though.

HD 650

Far more hollow and rounded. But a tad more natural. Smoother. And with more punch.

Treble

HD 650 > HD 700

HD 650's treble is just right with Sonarworks. HD 700 is a bit peaky and that takes time to adjust to. Note, the HD 700 isn't very bright. But the 650 is just more natural and balanced.

Transients, speed, articulation

HD 700 > HD 650

Not even a contest. There are really far apart here. The HD 650 is very good in its own right. But not of the same pedigree.

Timbre and tonality

HD 650 is a bit better than the HD 700 here.

Comfort

Don't get me wrong. The HD 650 is pretty comfortable on its own. However, although its sound is suitable for extended listening, it's comfort isn't exemplary. It is just good.

The HD 700 is probably the most comfortable headphone ever. More comfortable than the HD 800 I think. (I have tried the HD 800 twice.)

It is like going from average to superlative in terms of comfort. That alone justifies 2x the price for the HD 700.

Finally. Is the HD 700 a true upgrade to the HD 650?

Technically, yes. Definitely.

However, since the sound signature isn't exactly the same, subjective preferences may differ. Some may take one over the other.

But as far as technical prowess is concerned, the 700 definitely has an edge. And a definite one at that. And combined with the much better comfort, its price is justified. Without doubt.

Yes. I recommend the HD 700 over the HD 650 even at twice the price. But only if you feel the need for something that the HD 650 is unable to deliver. And ideally, you should try to audition before you buy it.

Update to Sennheiser HD 700's review

I have had a chance to listen to the HD 700 with two more setups:

Asus Essence One Muses DAC/Amp

iPad Mini 2 -> FiiO E12

I also compared it to the HD 650 with both setups.

The Fiio E12 setup sounds pretty good. With both cans. But not quite at the level of my previous setup or even the Asus E1 Muses.

I didn't do an AB test or DBT, so I can't be sure. And being an objectivist, I'm not sure why or whether there should be this kind of difference. But for some reason, the Asus setup sounds cleaner, clearer and less muffled.

The FiiO E12 is very good in its own right. And even with low gain I'm at about 12 o clock to get reasonably loud volume with either headphone.

HD 700 vs HD 650

After some more listening, I have come to realise that the HD 700 is a clear and very significant step up. And not only in terms of comfort.

The HD 700 is a lot cleaner, clearer, tighter, more articulate, faster and just gets the vocals a lot more right.

The HD 650 is still better for extended listening as the HD 700 does fatigue you after a while. But I've become used to HD 700's treble in under 72 hrs (and less than 2 hrs of use). It is not really fatiguing. But definitely a bit for extended listening. Unlike the HD 650.

Everything else goes in favour of the HD 700. You can hear a lot more detail. And the transients are a lot crisper as well.

The HD 650 does sound musical and lush. But vocals are relatively frighteningly real with the HD 700.

Honestly, I can't see much reason to choose the HD 650 over the HD 700 except for the smoother treble and better suitability for extended listening.

The HD 700 is difficult to use for over 20-40 minutes tops at a time. Unlike the HD 650. But that could be very personal. I couldn't listen to Soundmagic E80s for over 5 minutes tops. So maybe I'm just used to the less treble energetic HD 650.

Also, do note that most of these comparisons have been done while using the HD 650 with Sonarworks. So the HD 650 was dot neutral. In its stock form it is a bit too laid back for my tastes. And just can't compete with the HD 700.

Stuff like breath and air movements are something that really make the HD 700 shine. The HD 650 is okay here. But not in the same playing field.

The Fiio E12 does a good job with both the HD 700 and HD 650. But. I don't know why. I preferred the Asus Essence One Muses Edition with both the headphones.

Solid State vs Tube

For some reason, I always felt the HD 650 felt dead and cold with the Asus Essence One Muses edition. It felt lifeless. Like something was lacking.

However, the HD 700 also fares really well with this solid state amp. In fact, I preferred it with the Asus over my hybrid tube amp Project Ember, I think. I'm not sure though.

But. With the HD 650 I always chose Project Ember instead.

Now I'm really not sure why this is happening. I may have gone mad and maybe this is all placebo. But these are my findings so far...

P.S. Honestly, after listening to the HD 700 for a while, the HD 650 sounds like a distorted and muffled mess. The difference is at least as big if not bigger than moving from a HD 598 to a HD 650. The jump is probably a lot bigger in fact.

The HD 700 does better most of the stuff the HD 650 does well, and much better at that. But it is definitely a different presentation. And it is best to audition before you buy either!